1. Field of the Invention
The present invention relates to a route calculation system, a network management device, a route calculation engine, a route calculation method and a program product.
2. Description of Related Art
In a shortest route calculation system in a network, when a network management device sends a shortest route calculation request to a route calculation engine, the route calculation engine calculates the shortest route based on a shortest route calculation algorithm, and transmits the calculation result to the network management device. However, a conventional shortest route calculation algorithm does not have a concept of a layer hierarchy, and similarly treats both a link between same layers but a link between an upper layer and lower layer as a link merely. Therefore in a calculation of a shortest route of a multi-layer network, sometimes a wrong route is calculated.
As system which transmits a plurality of data through a same transmission route, there are a WDM (Wavelength Division Multiplexing) which transmits a plurality of data whose wavelength are different from each other, and a TDM (Time Division Multiplexing) which arranges a plurality of data in time sequence and transmits them. In some networks, a plurality of layers whose system are different exist, and multi-layer network is built. In these multi-layer network, there is a restriction condition resulting from striding a border between layers.
For example, in a border between an upper layer and a lower layer, as shown in FIG. 10, it is necessary to exchange the upper layer 201 and the lower layer 202. As shown in FIG. 11, when the upper layer 201 is a TDM network and the lower layer 202 is WDM network, a WDM communication device 203 includes a converter which includes transponders 210 which relays each TDM data, and a wavelength multiplexing/demultiplexing unit 211. Therefore the WDM communication device 203 can exchange the TOM network 201 and the WDM network 202. This converter performs an wavelength multiplexing to signal from the TDM network, and transmits the signal to the WDM network. Alternatively, the converter performs an wavelength demultiplexing to signal from the WDM network, and transmits the signal to the TDM network. The converter can transfer data from one TDM network to another TDM network. In this case, there is not a path like TDM-WDM-TDM physically, this become a restriction condition when a link is across a layer.
A conventional shortest route calculation algorithm does not have a concept of a layer hierarchy, and similarly treats both a link between same layers and a link between an upper layer and lower layer as a link merely. Therefore sometimes the aforementioned restriction condition is not satisfied, and a wrong route is determined.
In regard to a shortest route selection method which calculates a shortest route in a network, for example, a Patent Document 1 (Japanese Unexamined Patent Publication, First Publication No. 2006-165920) is known. The Patent Document 1 discloses that route information about a link which connects a domain of an initial point and a node of the initial point, a link which connects a domain of an end point and a node of the end point, a link which connects the domain of the initial point and the domain of the end point, and permutation of domains is stored.
However the shortest route selection method disclosed in the Patent Document 1 calculates a route only when layers are different between domains, and is not possible to calculate a route for multi-layer in a global network, without domain. In the Patent Document 1, a router is provided at a border between domains, and separates the border between layers. Therefore Patent Document 1 realizes calculation of a route. However, in the aforementioned multi-layer network, a router is not provided at a border between links.
As described above, in the conventional shortest route calculation algorithm does not have a concept of a layer hierarchy, and similarly treats both the link between same layers and the link between the upper layer and the lower layer. Therefore there is a problem in that sometimes a wrong route is determined.
Then in the multi-layer network, it is better to develop a shortest route calculation algorithm which satisfies the restriction condition for the multi-layer.
However the shortest route calculation algorithm which satisfies the restriction condition for the multi-layer needs to search a shortest route and to determine whether or not the restriction condition is satisfied. Therefore there is a problem that the algorithm become complicated.
The present invention is created in light of the aforementioned circumstances, and an object thereof is to provide a route calculation system, a network management device, a route calculation engine, a route calculation method and a program product capable of calculating a shortest route which satisfies a restriction condition of a multi-layer, without becoming complicating an algorithm for determining a shortest route, even in a multi-layer network.